1. Field of the Invention
The invention relates to methods, apparatus, and/or programming code means for determining the permeability of a fluid through a saturated material by measuring the dynamic response of that saturated material to shaking vibrations or shear wave propagation, and mapping data from said dynamic response to an invented alternative constitutive model that yields the property of permeability. Permeability may be described generally as the ease with which fluids can move through rock, soil, or other earth materials, and, therefore, the invented procedures, apparatus, and/or programming code means may be applied in oil well production, soil improvement, contaminated soils treatment, water well production, and/or landfill waste disposal, for example.
2. Related Art
Current non-seismic methods of permeability determination are limited to either laboratory tests (constant head or falling head), or to well tests like draw-down flow testing or drill stem testing in oil wells. The laboratory tests are restricted to small sample volumes and are not able to evaluate large samples with large grain sizes (ie: cobbles). Draw-down and other well flow tests are subject to skin affects and alterations of permeability within the invaded zone; for example, drilling muds can clog the formation in a zone near the borehole and lead to underestimation of permeability.
A number of existing seismic methods have been proposed in the prior art, however, their mathematical representations and procedures are different from those used in embodiments of the present invention. Such prior proposed methods can be quite complex, especially in the area of viscous representations, for example, the complex shear modulus. If a non-viscous “effective viscosity” is employed, it results in a complex modulus with a constant imaginary part. “Effective viscosity” is a concept that has its origins in past work with air saturated samples or seismic data of inadequate bandwidth; there are no materials know to possess “effective viscosity”. The preferred embodiments, on the other hand, comprise “truly viscous” representations (frequency dependent imaginary part for the shear modulus opposed to a constant) rather than “effective viscosity.”
One example of prior methods in the patent literature is Yamamoto, et al., (U.S. Pat. No. 5,142,500, 1992), which describes “Non-destructive method of measuring physical characteristics of sediments.” Yamamoto is a cross-well-specific patent, uses hydrophones and compressional waves, does not distinguish between coupled and uncoupled motion, and is for P-waves (not S-waves). The preferred embodiments of the present invention, on the other hand, may use shear waves and inertial effects, but not compression, to force fluids through the pores.
Another example of prior methods in the patent literature is Goloshubin, et al. (U.S. Pat. No. 7,136,757, 2006), which describes “Frequency-dependent processing . . . fluid saturated reservoirs.” Goloshubin is based on reflected P-waves, whereas the preferred embodiments of the present invention use shear-waves and transmission effects.
Further differences between preferred embodiments of the invention and the prior art may be found in the area of mapping of viscosity to permeability, and in that the present invention preferably predicts two possible mappings to permeability, coupled and uncoupled. Unlike prior art seismic methods known to the inventor, the methods of the preferred embodiments are both internally consistent and directly related to known laws of physics rather than dependent on empirical calibrations.
Further objects of some embodiments of the invention may comprise: sensing beyond the invaded zone, via shear-wave damping methods; extension to non-invasive applications; or applications for shallow, near-surface engineering problems, for example, comprising Love wave inversion for permeability.
These, and/or other, features and objects may be realized by embodiments of the invention, as will be understood by one of skill in the art after viewing the following description and attached Figures.